Zr/Nb Systematics of Ocean Island Basalts Reassessed--the Case for Binary Mixing |
| |
| Authors: | KAMBER B S; COLLERSON K D |
| |
| Institution: | 1DEPARTMENT OF EARTH SCIENCES, UNIVERSITY OF QUEENSLAND, ST LUCIA CAMPUS, BRISBANE, QLD 4072, AUSTRALIA |
| |
| Abstract: | A survey of global ocean island basalt geochemistry shows aremarkably strong linear correlation (average r2 = 0·95)between Zr and Nb concentrations. Fractional crystallizationexplains neither the range in Zr and Nb concentrations nor thefact that regression lines have intercepts significantly differentfrom zero. A substantial, linearly correlated (average r2 =0·92) variability in Zr and Nb concentrations remainsin the datasets after correction for fractional crystallization.Linear correlation between Zr and Nb concentrations is not expectedfrom variable degrees of melting because the concentration ofNb is significantly more sensitive to the degree of meltingthan that of Zr. Our main conclusion is that the Zr/Nb systematicsof ocean island basalts requires binary mixing, and more specificallymixing of two separate melts. We show that a mid-ocean ridgebasalt melt is the depleted endmember, common to all examinedocean island basalts. The enriched endmember has a very variableZr/Nb ratio. We speculate that, rather than implying the existenceof several distinct enriched reservoirs, the highly variableZr/Nb ratio could reflect intra-mantle processes such as fertilizationby small-degree melts or carbonate–silicate melt immiscibility. KEY WORDS: binary mixing; degree of melting; fractional crystallization; linear concentration relationship; trace element enrichment |
| |
| Keywords: | |
| 本文献已被 Oxford 等数据库收录！ |
|
